Campbell-Tennant, D.J.E., Gardner, J.L., Kearney, M.R. & Symonds, M.R.E. (2015) Climate related spatial and temporal variation in bill morphology over the past-century in Australian parrots. Journal of Biogeography 42: 1163-1175 PDF
What’s is about?
In this paper we show that not only do parrots that live in warmer climates in Australia have larger bills (most likely in order to help shed excess heat loads), but that in four of the five species we examined (mulga parrots, gang-gang cockatoos, red-rumped parrots and crimson rosellas) there has been an increase in bill size since 1871. By using museum specimens collected over the past 145 years, we found a between 4 and 10% increase in bill surface area over that time. These changes are consistent with the increases in climatic temperature experience over the past century, although the patterns may also indicate the influence of other facts such as changes in habitat or food availability.
What’s the story behind it?
When Glenn Tattersall and I published our paper in 2010 that showed birds that live in warmer climates tend to have bigger bills, we received a fair bit of media interest. One interview was with local ABC breakfast radio host, and former rock star, Red Symons (no relation), who asked a question that had occurred to us “does this mean bird beaks are going to get bigger with climate change”. We didn’t know the answer, but it’s a good question. His solution for how we would investigate this was also interesting “could you look at pictures or drawings of birds from old folios and see if the beaks were smaller then than they are now”. That wouldn’t really have been practical (or scientifically great), but of course museums have better than pictures – they have actual specimens stored for many years. Consequently, I combined with Janet Gardner (Monash University and ANU), whose published work on the effects of climate change on body size in birds, to ask this question. We took on, as a pilot study, an honours student, Dan Campbell-Tennant, who went on travels and measured lots of specimens of five parrot species. The results were even more intriguing than we anticipated – clear temporal and spatial trends. The big question now, is how widespread is this? We shall see….
The Symonds Lab 
[…] analysis of Australian parrots by our joint honours student Dan Campbell-Tennant (published as Campbell-Tennant et al. 2015). The work, done by Karensa McElroy of CSIRO was seeking to see if genetic diversity in mulga […]
[…] We looked at Australian museum collections of eight species of whistlers and shrike-thrushes in Australia to see whether there was any geographic and temporal variation in their bill and tarsus size in a way that fitted with Allen’s rule (bigger appendages in warmer climates). While we found a latitudinal pattern in four species in bill size that fits with Allen’s rule, there was no evidence for the rule in tarsus length. Furthermore there was not indication of a clear link to climate, no of any change in bill size and tarsus size over time that might suggest climate change is driving the evolution of larger appendages in these species, unlike a previous study by us (Campbell-Tennant et al. 2015). […]
[…] warming. We identify multiple examples of this phenomenon from the bills of Australian parrots (some of our previous work), to the wings of bats and tails of shrews. This is because these appendages enable animals to shed […]